Here's a direct link to the "closures" page at the aforementioned website. I believe it's got updates from members, so the caveat is it may not be 100% accurate, but it seems to be close.
I hope they don't mind?
https://www.campendium.com/camping/covid-19-state-by-state-campground-closures-responses/?utm_source=Campendium&utm_campaign=769dae5405-03-18-2020&utm_medium=email&utm_term=0_d42c2750af-769dae5405-112675385MODERATOR'S EDIT: Per the site Admin's request, I am closing all COVID-19 threads and directing future comments to one thread in Around the Campfire: 2019–20 CORONAVIRUS PANDEMIC POSTINGS